One known method for building a non-separating rotational body consists of providing a pipe mantle with tangential air inlet channels or air inlet slits. This creates a potential vortex which flows off axially. It was found, however, that vortex backflow zones in a potential vortex have poor stability properties. In order to create stable vortex backflow zones, the axial profile of the vortex stream created by the rotational body must have few rotations in the center, i.e. on the burner axis, and must have an excess axial velocity there. These considerations, i.e. to combine the advantages of a potential vortex and a rotational body that is perfect in terms of flow mechanics, have resulted in a burner according to EP-B1-0 321 809.
There is a risk with this burner, especially if operated with liquid fuel, that the flame can wander inside the burner, i.e. any time the axial speed in the center falls below a certain value. Then the flame can spread unhindered against the flow direction. The flame then wanders into the burner, usually creating overheating problems as a result. The generation of a rotational flow field has an important influence on creating a backflow zone, also called a backflow bubble, at the burner outlet. The generation of the rotational flow field requires that the stream be enclosed in an axially rotation-symmetrical space, which creates a "tube-shaped" zone especially in the center which is susceptible to a flame backflash in the counter-flow direction.